Pulse Generator wires reading 11 volts

[tkocher92]

I've been having this issue on a few bikes with no spark so far.

One common ground is that they all are reading 11 volts on both primary wires to the coil. I understand that one should read around 11-12v, and the wire coming from the cdi pulse should remain at zero.

Is this is a possible short in the CDI or the harness? I'm pretty stumped by this one.

[WintrSol]

One common ground is that they all are reading 11 volts on both primary wires to the coil. I understand that one should read around 11-12v, and the wire coming from the cdi pulse should remain at zero.

Not sure where you got that understanding, nothing is said about it in the FSM. And, from the functional diagram, I would expect both wires to be nearly the same (electronics engineer here). What is important is the Ohms measurement of the coil, which the FSM says should be 50-200 Ohms. Also, any metal stuck on or around the coil can and will reduce the signal level, so the area should be inspected for any kind of fouling. Contact resistance of the connectors between the igniter and coil is also a potential problem.

[Herb]

I am not very versed on the 800 but my 1400s will almost never fire if the battery voltage is 11 vdc or under.

The power wire to the coils should read battery voltage, or close to it. If they are at 11 vdc when not cranking it will probably be less than 10 when cranking and when the voltage is that low the many engines won't have enough volts to fire plugs under compression.

If the battery is at 11 vdc it is too low. If the battery voltage is markedly higher than the coil wire there is a bad connection in the wiring to the coils, usually corrosion in one of the switches or on connectors.

[WintrSol]

I guess I should have asked, "Which coil, the timing pickup coil, or the spark coil?" I just assumed he meant the timing pickup coil.

[Herb]

I guess I should have asked, "Which coil, the timing pickup coil, or the spark coil?" I just assumed he meant the timing pickup coil.

I did too, at first, but then I got to thinking that there is no primary on the pulse gen coils...

Also, the comment about the CDI trigger wire. The ignition box provides a ground to the coil.

I am not sure if the trigger wire is constantly grounded until the bike turns over but it is the loss of the ground that causes the coil to make spark. Pulling the trigger wire off should show close to battery voltage potential on the ground side of the coil. Grounding and breaking the trigger wire will cause a spark.

From my experience with the 1400s anything less than 10 vdc, while cranking, at the coil power wire will result in no spark under compression.

[WintrSol]

Battery Voltage requirement for the VS800 is about the same - too low and no spark.
The simplified diagram in the FSM shows the pickup coils connected only to the igniter, and looks to me like a differential input; if true, both wires would float to the level of the input circuit, no ground on either. This would allow for a smaller pulse over a single-ended system. But, the polarity of the coil inputs seems important for proper operation, too, which would argue for a virtual ground on one. I really can't tell without putting an oscilloscope on them, which I was never inspired to do before I sold my 800.

[Herb]

Battery Voltage requirement for the VS800 is about the same - too low and no spark.
The simplified diagram in the FSM shows the pickup coils connected only to the igniter, and looks to me like a differential input; if true, both wires would float to the level of the input circuit, no ground on either. This would allow for a smaller pulse over a single-ended system. But, the polarity of the coil inputs seems important for proper operation, too, which would argue for a virtual ground on one. I really can't tell without putting an oscilloscope on them, which I was never inspired to do before I sold my 800.

I don't know how hard the 800 cranks but on a warm day with a cold engine my 1400 will have a battery voltage of 12.5vdc and when I start cranking the voltage initially drops to about 9vdc and then comes back up to about 11vdc while still cranking.

The pulse generators only give a signal to the ignitor box, the box itself provides a ground to the ign coil when the box gets a signal it opens the ground and causes the coil to work. Not sure of the actual internal workings of the ignition box as to the actual way it does it.

I have read that many of the pulse generators are actually just a transistor that is providing a ground and when the system is triggered, usually using a magnetic impulse, it turns off the transistor breaking the ground. However, in the 1400 and, I assume, the 800 the ignition box reads engine rpm and varies the timing so there is some circuitry that does that, so the pulse generator uses a small current to signal the ign box to break the ground.